The art of plating zinc onto a moving metal strip is well developed. Normally, a consumable anode is provided in the plating cell so that the zinc forming the anode is electrically deposited on the moving strip which is connected to a negative D.C. potential with respect to the anode. Representative patents illustrating this concept are U.S. Pat. Nos. 2,382,018; 2,509,304; 2,569,577; 2,690,424; and U.S. Pat. No. RE 23,456. In some instances, the anode is non-consumable and the electrolyte is provided with the zinc compound which provides zinc ions for electrolysis. Representative patents showing non-consumable anodes for use in electroplating are U.S. Pat. Nos. 3,354,070 and 3,483,113. In many instances, the strip is moved longitudinally through one or more plating traps which include an electrolyte and are continuously provided with electrolyte from a lower reservoir into which the electrolyte overflows from the tray. In this manner, an elongated line of trays can be used to plate the desired thickness of material onto a moving strip. Generally, the anodes are provided in the tray and the strip is provided with a negative potential. A representative patent showing this general concept is U.S. Pat. No. 3,468,783. Another patent showing the tray arrangement is U.S. Pat. No. 3,287,238. The current density of the plating process determines the rate at which zinc or other metal is placed onto the strip. As the current density is increased, the plating process is more rapid and the speed of processing of a metal strip is increased. This reduces the length of the line used to obtain a given thickness of plated material or increases the speed at which the strip can be passed through the apparatus during the plating process. Generally, a current density of between 500-2000 ampers per square meter are common. To increase the current density, it is known to increase the velocity of the electrolyte along the strip as shown in U.S. Pat. No. 3,975,242 wherein the strip is passed through a narrow vessel and the electrolyte is passed through this same vessel.
The above discussion is the general background of the present invention and the patents mentioned above are incorporated by reference for the illustrated background information.
The prior art described above does not illustrate a plating device or apparatus wherein one or both sides of a strip can be selectively plated in a tray type plating device using a non-consumable anode and capable of current densities substantially greater than the normal current densities of 500-2000 ampers per square meter. Also, the prior art discussed above does not illustrate a non-consumable anode for use in a tray type of plating process wherein the anode is economical to produce, allows high current densities and produces uniform results across the width of the strip.